Intermittent starting??? 1994 LS400

cabbos · February 6, 2016

Hi all hope someone can shed some light on a very annoying problem, it started a couple of weeks ago drove car about 6-8 miles stopped done my chores go back in car and wouldn't start. Turns over but not firing called AA he found there was no power to fuel pump (saying suspect fuel pump relay). he them put a power probe on blue wire to fuel pump and bingo it started :). followed me home, got home turned it off and on you guessed it nothing! turns over but not starting.

So then i went to Local main dealer who said no not fuel pump relay (does not have one on my model?, its the starter relay) but very much doubts it more likely to be fuel pump £500+ labour (don't think so) why would it start when powered directly from Battery?. I have tried another starter relay and made no difference when i use the power probe it works. Can anyone HELP don't want to get rid of car, does anyone know of a relay somewhere else?. i have also tried swapping other relays around still nothing and there was no warning to any problems before it was just something that happened overnight.

Thanks in advance for any help you can give.

cabbos · February 7, 2016

Update: I have tried to bridge fp and b+ (not starting). B+ does not seem to have 12v (when ignition on) also efi relay port does not have 12v (when ignition on) does anyone know why this is so?, where does the power come from ie : ecu etc help is needed (only as need car for holiday in 2 weeks 😳😳😳)

cabbos · February 8, 2016

Does anyone know why i am not getting power to my EFI relay in the fuse box?. Anyone pls Help

cabbos · February 16, 2016

Update, took car to an independent Toyota specialist he located fault to part of the ecu not sending 12v's to efi so now been bypassed with inline fuse, relay and resistors now car starts, goes and stops. 😀😀😀😀😀

steve2006 · February 17, 2016

Sorry I never saw this post until now or I would have tried to help.

A common problem with the ECU are the capacitors failing causing all sorts of strange problems, have a look on www.clublexus.com under the LS400 section and you will find all the infomation to repair the ECU.

Seems strange how the +B supply was missing at the test port, this is not ECU controlled.

https://www.google.co.uk/search?sclient=tablet-gws&client=safari&channel=ipad_bm&site=&source=hp&q=1994+lexus+ls400+fuel+pump+wiring&oq=1994+lexus+ls400+fuel+pump+wiring&gs_l=tablet-gws.3..0i22i30l2.5127.22140.0.23012.33.22.0.11.11.0.471.4163.1j15j3j1j2.22.0....0...1c.1.64.tablet-gws..0.31.3629.HWkH4aQ0j2s#imgrc=xLQ7PW3MGZCK1M%3A

cabbos · March 5, 2016

Thanks Steve just back from my hols, i must of printed out all the info i could get on the fuel pump and relay for some strange reason on trying to start up there was no 12v from +B and couldn't get diagnostic port to communicate to code reader once it started all ok? hence the bypass after that everything works as normal. He seemed to suspect that part of ecu is not communicating (maybe capacitors like what happens to dashboard lights?) might be at fault and as i needed car in a couple of days to get to airport i was more than happy for him to get it going.